The present invention relates generally to the targeting of diagnostic compounds to specific cells and tissues. The invention is more particularly related to targeting molecules for use in delivering compounds to epithelial tissue. Such targeting molecules may be used in a variety of diagnostic procedures.
To improve the diagnosis of cancer and other disorders, some researchers have used the systemic administration of imaging agents (e.g., proton relaxation agents as well as fluorescent chromophores) for contrast enhancement in techniques such as magnetic resonance imaging (MRI) and laser phototherapy. For example, tumor location using radiolabeled antibodies and handheld probes for intraoperative tumor detection has been attempted (Arnold et al., Surgery 112:624-631, 1992). Introduction of fluorescein conjugated antibodies for endoscopic tumor location (xe2x80x9cphoto-immunodiagnosisxe2x80x9d) in animals and in humans has also been attempted (Folli et al., Cancer Res. 54:2643-2450, 1994; Pelegrin et al., Cancer 67:2529-2535, 1994). In addition, fluorochrome-conjugated antibodies have been used to study antibody circulation in tumor microvasculature and biodistribution in tumors.
While such techniques show promise, their use has been limited by a lack of agents or conjugates that show specific localization to particular cell types. For example, localization to cell populations that are frequent sites of neoplastic development would aid in the diagnosis of incipient tumors. Further selectivity for neoplastic cells or macroscopic tumors would greatly aid in their localization and excision.
The ability to target imaging compounds to epithelial cells would enhance a variety of diagnoses, since such cells give rise to a wide spectrum of tumors, as well as viral and bacterial infections. Targeting of imaging compounds to epithelial cells would ideally delineate normal tissue from neoplastic lesions and potentially identify other types of lesions such as infections. Refinement of cell type specificity to be selective for the abnormal cells would further aid in localizing and treating those cells. However, no techniques are currently available for such targeting of imaging agents.
Accordingly, there remains a need in the art for systems for delivering imaging agents to target cells, particularly epithelial cells and cells or tissues bounded by epithelial cells. The present invention fulfills these needs and further provides other related advantages.
Briefly stated, the present invention provides targeting molecules for the specific delivery of imaging agents to epithelial cells and tissues. In several aspects, the present invention provides a targeting molecule linked to at least one imaging agent. In one such aspect, the targeting molecule comprises a polypeptide that (a) forms a closed covalent loop; and (b) contains at least three peptide domains having xcex2-sheet character, each of the domains being separated by domains lacking xcex2-sheet character; wherein the polypeptide is not a full length dimeric IgA. In specific embodiments, the polypeptide further contains one or more of the following additional domains: a fourth peptide domain having xcex2-sheet character, separated from other domains having xcex2-sheet character by a domain lacking xcex2-sheet character; a linear N-terminal domain; and a C-terminal domain, which may comprise a linear peptide having xcex2-sheet character and/or a covalently closed loop.
Within other such aspects, the targeting molecule comprises a sequence recited in any one of SEQ ID NO:1-SEQ ID NO:8 and SEQ ID NO:13.
In a further related aspect, the present invention provides a targeting molecule capable of specifically binding to a basolateral factor associated with an epithelial surface and causing the internalization of an imaging agent linked thereto, wherein the targeting molecule is not full length dimeric IgA.
Within another such aspect, the targeting molecule comprises a polypeptide that: (a) forms a closed covalent loop; and (b) contains at least three peptide domains having xcex2-sheet character, each of the domains being separated by domains lacking xcex2-sheet character; wherein the targeting molecule is linked to at least one imaging agent by a substrate for an intracellular or extracellular enzyme associated with an epithelial barrier, or by a side chain of an amino acid in an antibody combining site.
Within yet another such aspect, the targeting molecule comprises a polypeptide that: (a) forms a closed covalent loop; and (b) contains at least three peptide domains having xcex2-sheet character, each of the domains being separated by domains lacking xcex2-sheet character; wherein the imaging agent is not naturally associated with the targeting molecule, and wherein the imaging agent is not iodine.
Within another aspect, the present invention provides a pharmaceutical composition comprising a targeting molecule linked to at least one imaging agent as described above in combination with a pharmaceutically acceptable carrier.
In further aspects, methods are provided for diagnosing a disease in a patient, comprising (a) administering to a patient a pharmaceutical composition as described above; and (b) detecting the presence of imaging agent within the patient.
These and other aspects of the present invention will become apparent upon reference to the following detailed description and attached drawings. All references disclosed herein are hereby incorporated by reference in their entirety as if each was incorporated individually.